These functions are used to manage node
lists within the software 802.11 stack. These lists are typically
used for implementing host-mode AP functionality, or providing
signal quality information about neighbouring nodes.

The
ieee80211_node_attach() function is called from
ieee80211_ifattach(9) to initialize node database management
callbacks for the interface ifp (specifically for memory
allocation, node copying and node signal inspection). These
functions may be overridden in special circumstances, as long as
this is done after calling ieee80211_ifattach(9) and prior to any
other call which may allocate a node.

The
ieee80211_node_lateattach() function initialises the
ic_bss node element of the interface ifp during
ieee80211_media_init(9). This late attachment is to account for
certain special cases described under
ieee80211_node_attach().

The
ieee80211_node_detach() function destroys all node database
state associated with the interface ifp, and is usually
called during device detach.

The
ieee80211_begin_scan() function initialises the node
database in preparation of an active scan for an access point on
the interface ifp. The scan begins on the next radio channel
by calling ieee80211_next_scan() internally. The actual
scanning for an access point is not automated; the device driver
itself only handles setting the radio frequency of the card and
stepping through the channels.

The
ieee80211_next_scan() function is used to inform the
ieee80211(9) layer that the interface ifp is now scanning
for an access point on the next radio channel. A device driver is
expected to first call ieee80211_begin_scan(), to initialize
the node database, then set the radio channel on the device; then,
after a certain time has elapsed (200ms for example), call
ieee80211_next_scan() to move to the next channel.
Typically, a callout is used to automate this process; see
callout_init(9) for more information on how to use callouts.

The
ieee80211_create_ibss() function sets up the
net80211-specific portion of an interface’s softc, ic,
for use in IBSS mode.

The
ieee80211_end_scan() function is called by
ieee80211_next_scan() when the state machine has peformed a
full cycle of scanning on all available radio channels. Internally,
ieee80211_end_scan() will inspect the node cache associated
with the interface ifp for suitable access points found
during scanning, and associate with one, should the parameters of
the node match those of the configuration requested from
userland.

The
ieee80211_alloc_node() function allocates an instance of
struct ieee80211_node for a node having the MAC address
macaddr, and associates it with the interface ic. If
the allocation is successful, the node structure is initialised by
ieee80211_setup_node(); otherwise, NULL is returned.

The
ieee80211_dup_bss() function is similar to
ieee80211_alloc_node(), but is instead used to create a node
database entry for the BSSID macaddr associated with the
interface ic. If the allocation is successful, the node
structure is initialised by ieee80211_setup_node();
otherwise, NULL is returned.

The
ieee80211_find_node() function will iterate through the node
list associated with the interface ic, searching for a node
entry which matches macaddr. If the entry is found, its
reference count is incremented, and a pointer to the node is
returned; otherwise, NULL will be returned.

The
ieee80211_lookup_node() function is similar to
ieee80211_find_node(), with an additional argument
chan which is used to specify a channel for the match. If
the entry is found, its reference count is incremented, and a
pointer to the node is returned; otherwise, NULL will be
returned.

The
ieee80211_free_node() function will remove the node
ni from the node database entries associated with the
interface ic, and free any memory associated with the node.
This private method can be overridden in
ieee80211_node_attach().

The
ieee80211_free_allnodes() function will iterate through the
node list calling ieee80211_free_node() for all nodes
associated with the interface ic.

The
ieee80211_timeout_nodes() checks if the inactivity timer of
each node associated with the interface ic has exceeded the
pre-defined constant IEEE80211_INACT_MAX. If so, then the node is
freed, after sending a deauthentication message.

The
ieee80211_iterate_nodes() function will call the
user-defined callback function f for all nodes in the node
database associated with the interface ic. The callback is
invoked with the with the user-supplied value arg and a
pointer to the current node.

SEE ALSO

ieee80211(9), ifnet(9)

HISTORY

The ieee80211 series of functions
first appeared in NetBSD 1.5, and were later ported to
FreeBSD 4.6.

AUTHORS

This manual page was written by Bruce M.
Simpson 〈bms@FreeBSD.org〉 and Darron Broad
〈darron@kewl.org〉.